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podman-compose/docs/Extensions.md

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Podman specific extensions to the docker-compose format

Podman-compose supports the following extension to the docker-compose format. These extensions are generally specified under fields with "x-podman" prefix in the compose file.

Container management

The following extension keys are available under container configuration:

  • x-podman.uidmaps - Run the container in a new user namespace using the supplied UID mapping.

  • x-podman.gidmaps - Run the container in a new user namespace using the supplied GID mapping.

  • x-podman.rootfs - Run the container without requiring any image management; the rootfs of the container is assumed to be managed externally.

  • x-podman.no_hosts - Run the container without creating /etc/hosts file

For example, the following docker-compose.yml allows running a podman container with externally managed rootfs.

version: "3"
services:
    my_service:
        command: ["/bin/busybox"]
        x-podman.rootfs: "/path/to/rootfs"

For explanations of these extensions, please refer to the Podman Documentation.

Secrets

The following extension keys are available under secret configuration:

x-podman.relabel - Configure SELinux relabeling

For example, the following configures custom-secret to use mount with private and unshared content. Only the current container can use a private volume.

secrets:
  custom-secret:
    x-podman.relabel: Z

For explanations of these extensions, please refer to the podman-run --volume documentation).

Network management

The following extension keys are available under network configuration:

  • x-podman.disable-dns - Disable the DNS plugin for the network when set to 'true'.
  • x-podman.dns - Set nameservers for the network using supplied addresses (cannot be used with x-podman.disable-dns`).

For example, the following docker-compose.yml allows all containers on the same network to use the specified nameservers:

version: "3"
network:
  my_network:
    x-podman.dns:
      - "10.1.2.3"
      - "10.1.2.4"

For explanations of these extensions, please refer to the Podman network create command Documentation.

Per-network MAC-addresses

Generic docker-compose files support specification of the MAC address on the container level. If the container has multiple network interfaces, the specified MAC address is applied to the first specified network.

Podman-compose in addition supports the specification of MAC addresses on a per-network basis. This is done by adding a x-podman.mac_address key to the network configuration in the container. The value of the x-podman.mac_address key is the MAC address to be used for the network interface.

Note that the compose spec now supports mac_address on the network level, so we recommend using the standard mac_address key for setting the MAC address. The x-podman.mac_address is still supported for backwards compatibility.

Specifying a MAC address for the container and for individual networks at the same time is not supported.

Example:

---
version: "3"

networks:
  net0:
    driver: "bridge"
    ipam:
      config:
        - subnet: "192.168.0.0/24"
  net1:
    driver: "bridge"
    ipam:
      config:
        - subnet: "192.168.1.0/24"

services:
  webserver:
    image: "busybox"
    command: ["/bin/busybox", "httpd", "-f", "-h", "/etc", "-p", "8001"]
    networks:
      net0:
        ipv4_address: "192.168.0.10"
        x-podman.mac_address: "02:aa:aa:aa:aa:aa"
      net1:
        ipv4_address: "192.168.1.10"
        mac_address: "02:bb:bb:bb:bb:bb" # mac_address is supported

Per-network interface name

Using x-podman.interface_name within a containers network config you can specify the interface name inside the container.

Podman-specific network modes

Generic docker-compose supports the following values for network-mode for a container:

  • bridge
  • host
  • none
  • service
  • container

In addition, podman-compose supports the following podman-specific values for network-mode:

  • slirp4netns[:<options>,...]
  • ns:<options>
  • pasta[:<options>,...]
  • private

The options to the network modes are passed to the --network option of the podman create command as-is.

Docker Compose Compatibility

podman-compose aims to be compatible with docker-compose, but there are some differences in behavior and features. The following sections describe how to enable compatibility with docker-compose and how to handle some of the differences.

Compatibility settings can either be set explicitly as described below, or by setting the docker_compose_compat meta settings to true under the global x-podman key:

x-podman:
    docker_compose_compat: true

This will enable all compatibility settings described below, and is equivalent to setting each of them to true.

This setting can also be changed by setting the PODMAN_COMPOSE_DOCKER_COMPOSE_COMPAT environment variable.

Compatibility of name separators between docker-compose and podman-compose

Currently, podman-compose is using underscores (_ character) as a separator in names of containers, images, etc., while docker-compose has switched to hyphens (- character). This setting allows to switch podman-compose to use hyphens as well.

To enable compatibility between docker-compose and podman-compose, specify name_separator_compat: true under global x-podman key:

x-podman:
    name_separator_compat: true

By default name_separator_compat is false. This will change to true at some point and the setting will be removed.

This setting can also be changed by setting PODMAN_COMPOSE_NAME_SEPARATOR_COMPAT environment variable.

Compatibility of default network names between docker-compose and podman-compose

Current versions of podman-compose may produce different default external network names than docker-compose under certain conditions. Specifically, docker-compose removes dashes (- character) from project name.

To enable compatibility between docker-compose and podman-compose, specify default_net_name_compat: true under global x-podman key:

x-podman:
    default_net_name_compat: true

By default default_net_name_compat is false. This will change to true at some point and the setting will be removed.

This setting can also be changed by setting PODMAN_COMPOSE_DEFAULT_NET_NAME_COMPAT environment variable.

Compatibility of default network behavior between docker-compose and podman-compose

When there is no network defined (neither network-mode nor networks) in service, The behavior of default network in docker-compose and podman-compose are different.

Top-level networks podman-compose docker-compose
No networks default default
One network named net0 net0 default
Two networks named net0, net1 podman(--network=bridge) default
Contains network named default default default

To enable compatibility between docker-compose and podman-compose, specify default_net_behavior_compat: true under global x-podman key:

x-podman:
    default_net_behavior_compat: true

This setting can also be changed by setting PODMAN_COMPOSE_DEFAULT_NET_BEHAVIOR_COMPAT environment variable.

Custom pods management

Podman-compose can have containers in pods. This can be controlled by extension key x-podman in_pod. It allows providing custom value for --in-pod and is especially relevant when --userns has to be set.

For example, the following docker-compose.yml allows using userns_mode by overriding the default value of --in-pod (unless it was specifically provided by "--in-pod=True" in command line interface).

version: "3"
services:
    cont:
        image: nopush/podman-compose-test
        userns_mode: keep-id:uid=1000
        command: ["dumb-init", "/bin/busybox", "httpd", "-f", "-p", "8080"]

x-podman:
    in_pod: false

This setting can also be changed by setting PODMAN_COMPOSE_IN_POD environment variable.

It is also possible to override the default arguments for pod creation that are used when --pod-args is not passed on the command line:

version: "3"
services:
    cont:
        image: nopush/podman-compose-test
        command: ["dumb-init", "/bin/busybox", "httpd", "-f", "-p", "8080"]
x-podman:
    pod_args: ["--infra=false", "--share=", "--cpus=1"]

When not set in docker-compose.yml or on the command line, the pod args default to ["--infra=false", "--share="].

This setting can also be changed by setting PODMAN_COMPOSE_POD_ARGS environment variable.